1. Field of the Invention
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a rotary-type polishing apparatus which allows a polishing pad to be automatically replaced without stopping rotary or circulatory motion of a polishing table.
2. Description of the Related Art
Recent rapid progress in semiconductor device integration demands smaller and smaller wiring patterns or interconnections and also narrower spaces between interconnections which connect active areas. One of processes available for forming such interconnections is photolithography. Though a photolithographic process can form interconnections that are at most 0.5 xcexcm wide, it requires that surfaces on which pattern images are to be focused by a stepper be as flat as possible because depth of focus of an optical system is relatively small.
It is therefore necessary to make surfaces of semiconductor wafers flat for photolithography. One customary way of flattening surfaces of semiconductor wafers is to polish them with a polishing apparatus, and such a process is called Chemical Mechanical Polishing (CMP) in which semiconductor wafers are chemically and mechanically polished while supplying a polishing liquid comprising abrasive grains and chemical solution such as alkaline solution.
In a manufacturing process of a semiconductor device, a thin film is formed on a semiconductor device, and then micromachining processes, such as patterning or forming holes, are performed thereon. Thereafter, the above processes are repeated to form thin films on the semiconductor device. Recently, semiconductor devices have become more integrated, and structure of semiconductor elements has become more complicated. In addition, the number of layers in multilayer interconnections used for a logical system has been increased. Therefore, irregularities on a surface of a semiconductor device are increased, so that step height on the surface of the semiconductor device becomes larger.
When irregularities of a surface of a semiconductor device are increased, the following problems arise. Thickness of a film formed in a portion having a step is relatively small. An open circuit is caused by disconnection of interconnections, or a short circuit is caused by insufficient insulation between layers. As a result, good products cannot be obtained, and yield is lowered. Further, even if a semiconductor device initially works normally, reliability of the semiconductor device is lowered after a long-term use.
Thus, during a manufacturing process of a semiconductor device, it is increasingly important to planarize a surface of the semiconductor device. The most important one of planarizing technologies is chemical mechanical polishing (CMP). During chemical mechanical polishing, a polishing apparatus is employed. While a polishing liquid containing abrasive particles such as silica (SiO2) therein is supplied onto a polishing surface such as a polishing pad, a substrate such a semiconductor wafer is brought into sliding contact with the polishing surface, so that the substrate is polished.
FIGS. 16 and 17 of the accompanying drawings show a conventional polishing apparatus for carrying out a CMP process. As shown in FIGS. 16 and 17, the conventional polishing apparatus comprises a polishing table 102 having a polishing pad (polishing cloth) 100 attached to its upper surface, a motor 104 for rotating the polishing table 102, and a vertically movable top ring 106 for holding a substrate W such as a semiconductor wafer with its surface, to be polished, facing the polishing pad 100. While the polishing table 102 and the top ring 106 are being rotated independently about their own axes, the substrate W is pressed against the polishing pad 100 under a constant pressure by the top ring 106, and a polishing liquid is supplied from a nozzle (not shown) to the polishing pad 100, thereby polishing the surface of the substrate W to a flat mirror finish. The polishing liquid comprises fine abrasive particles of silica or the like suspended in an alkaline solution or the like. The substrate W is polished by a chemical mechanical polishing action which is a combination of a chemical polishing action performed by the alkaline solution and a mechanical polishing action performed by the abrasive particles of silica or the like.
The polishing pad 100 is usually regenerated by a dresser which comprises a nylon brush, diamond particles, or the like. When the polishing pad 100 is worn to an extent that its polishing capability can no longer be restored by the dresser, the polishing pad 100 is replaced with a new one.
The polishing pad 100 is generally attached to an upper surface of the polishing table 102 by an adhesive tape. For replacing the polishing pad 100 with a new one, it is necessary to temporarily stop a CMP process, and a skilled operator is required to peel off the polishing pad 100 and attach a new polishing pad 100 to the polishing table 102.
FIG. 18 of the accompanying drawings shows another conventional polishing apparatus for eliminating the above drawbacks. The polishing apparatus shown in FIG. 18 has a polishing pad 100 attached to a polishing table 102 under vacuum developed by a vacuum attraction section 108 provided in the polishing table 102. Since the polishing pad 100 is removed from the polishing table 102 by releasing the vacuum, the polishing pad 100 can easily and quickly be replaced with a new one. However, replacing the polishing pad 100 requires temporarily stopping a CMP process because the polishing pad cannot be replaced while the polishing pad table 102 is rotating.
Still another conventional polishing apparatus is shown in FIG. 19 of the accompanying drawings. In FIG. 19, a polishing table 110 is fixed in position, and a pair of rolls 112, 114 are rotatably disposed one on each side of the polishing table 110. An elongate polishing pad 116 wound onto the roll 112 is continuously fed at a constant speed along an upper surface of the polishing table 110, and beneath a substrate W, toward the other roll 114 onto which the polishing pad 116 is wound. The substrate W is polished by the elongate polishing pad 116 as the polishing pad travels over the polishing table 110 in one direction. Principles of the polishing apparatus shown in FIG. 19 are not applicable to a rotary-type polishing apparatus in which a polishing table makes rotary or circulatory motion.
It is therefore an object of the present invention to provide a rotary-type polishing apparatus which has a polishing table that makes rotary or circulatory motion, and which allows a polishing pad to be automatically replaced without stopping a CMP process.
Another object of the present invention is to provide a polishing apparatus which has a polishing table that makes predetermined motion, and which allows a polishing pad to be automatically replaced without stopping a CMP process.
According to a first aspect of the present invention, there is provded a polishing apparatus comprising: a polishing table for making rotary or circulatory motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a pair of rolls rotatable about their own axes and movable in unison with the polishing table; and a polishing pad which is wound on one of the rolls and supplied over an upper surface of the polishing table toward the other of the rolls.
Even when the polishing table is in rotary or circulatory motion, the polishing pad can be transported from one of the rolls over the upper surface of the polishing table toward the other roll by a distance corresponding to a region of the polishing pad that has been used to polish workpieces. A used region of the polishing pad can thus automatically be replaced with a new region thereof.
In a preferred aspect of the present invention, the polishing table has an attraction section for attracting and holding the polishing pad to the polishing table.
In a preferred aspect of the present invention, the polishing apparatus further comprises a roll motor connected to at least the other of the rolls, wherein the roll motor is controllable in a wireless or wired fashion. When a signal is transmitted to the roll motor to energize the roll motor to rotate the rolls, a used region of the polishing pad can automatically be replaced with a new region thereof.
In a preferred aspect of the present invention, the polishing pad comprises one of a polyurethane foam pad, a suede type pad, and a fixed abrasive pad comprising abrasive particles embedded therein.
In a preferred aspect of the present invention, the polishing apparatus further comprises a sensor for detecting surface roughness of the polishing pad.
In a preferred aspect of the present invention, the polishing apparatus further comprises a sensor for detecting surface for detecting surface roughness of the polishing pad, and the roll motor is energized on the basis of a detection signal of the sensor.
In a preferred aspect of the present invention, the polishing pad comprises a plurality of sub-pads which are divided along a take-up direction of the polishing pad.
According to a second aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; and a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table.
According to the second aspect of the present invention, the polishing pad is supplied from the polishing pad supply device, and the supplied polishing pad is held by the polishing pad holding device and placed in an elongate state on the polishing table. Thus, even if the polishing table is in motion, a used region of the polishing pad can thus automatically be replaced with a new region of the polishing pad.
In a preferred aspect of the present invention, the polishing pad supply device comprises a supply roll onto which the elongate polishing pad is wound.
In a preferred aspect of the present invention, the polishing pad holding device comprises a take-up roll onto which the elongate polishing pad is to be wound.
In a preferred aspect of the present invention, the polishing table has an attraction section for attracting and holding the polishing pad to the polishing table.
In a preferred aspect of the present invention, the polishing apparatus further comprises a roll motor connected to the take-up roll, wherein the roll motor is controllable in a wireless or wired fashion.
In a preferred aspect of the present invention, the predetermined motion of the polishing table is one of rotary motion, circulatory motion, and linear reciprocating motion.
According to a third aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and a sensor for detecting surface roughness of the polishing pad.
According to a fourth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and a brush for removing from the polishing pad ground-off material produced during a polishing process.
According to a fifth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and an atomizer for spraying a gas-liquid mixture onto the polishing pad.
According to a sixth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from the polishing pad supply device and placing the polishing pad such that the polishing pad makes predetermined motion integrally with the polishing table; and an eddy-current sensor for monitoring thickness of a film of the workpiece.
According to a seventh aspect of the present invention, there is provided a polishing apparatus comprising:
a first polishing table which mounts a polishing pad on a surface of the first polishing table, wherein the polishing pad being is held by at least two rolls disposed around the first polishing table; and
a second polishing table which mounts a polishing pad on a surface of the second polishing table, wherein the polishing pad is held by at least two rolls disposed around the second polishing table.
According to an eighth aspect of the present invention, there is provided a polishing apparatus comprising:
a first polishing table which mounts a polishing pad on a surface of the first polishing table, wherein the polishing pad is held by at least two rolls disposed around the first polishing table; and
a second polishing table which mounts a polishing pad on a surface of the second polishing table, wherein the polishing pad is held by at least two rolls disposed around the second polishing table, wherein respective shafts of the rolls are substantially parallel to a polishing surface of the polishing pad.